CN102928839A - Full-aperture imaging method for multi-channel wave beam-pointing synthetic aperture radar (SAR) - Google Patents

Abstract

The invention discloses a full-aperture imaging method for multi-channel wave beam-pointing synthetic aperture radar (SAR), and mainly solves the problem of low imaging resolution in a wide scene. The full-aperture imaging method comprises the following implementation processes of: (1) receiving original SAR echo signals in a full-aperture way in a one-transmitting multi-receiving channel mode; (2) performing azimuth bandwidth compressing processing and wave beam compressing processing on the echo signals; (3) recovering and reconstructing the compressed echo signals by a Doppler space-time adaptive post-processing method; (4) transforming the recovered and reconstructed echo signals into a two-dimensional frequency domain; and (5) performing distance migration correction and pulse compression on the echo signals in the two-dimensional frequency domain by utilizing a Doppler imaging algorithm to realize imaging. According to the method, the azimuth resolution is improved by utilizing the wave beam-pointing SAR; the problem that the bandwidth of the wave beam-pointing SAR is over-wide is solved by compressing a wave beam domain and an angle domain; simultaneously, an imaging processing flow is simplified; the imaging processing efficiency is improved; and the method can be used in the SAR imaging of a space-borne platform under the requirements of wide scene and high resolution.

Description

The full aperture formation method of hyperchannel beam position SAR

Technical field

The invention belongs to radar signal processing field, particularly the full aperture formation method of hyperchannel beam position synthetic-aperture radar SAR is applicable to Space-borne SAR imaging processing.

Background technology

In the Spaceborne SAR System of routine, the orientation high resolving power require to improve the orientation bandwidth, after the orientation bandwidth improves, need a larger orientation sampling rate PRF avoid the orientation to fuzzy.And large scene area coverage requires a less PRF, does not overlap in order to guarantee adjacent echo sequence.Therefore, being observed the azimuthal resolution of scene and the size of scene is conflict.

For guarantee large observation scene and solve the orientation to fuzzy problem, hyperchannel SAR system has been proposed.In the hyperchannel SAR system, PRF usually can be less than the aspect bandwidth, will cause like this orientation to fuzzy, so must carry out the restoration and reconstruction of bearing signal.The bearing signal restoration methods of hyperchannel SAR mainly is two large classes at present: first kind method is from the angle of Signals ﹠ Systems, and the system transfer function of utilization is described multi-channel system, then recovers the mixed signal that falls of nothing by the concept of inverse system; The concept of Equations of The Second Kind method integrated array from Radar Imaging Processing is processed, and by analyzing the different fuzzy physical significances of frequency in integrated array, the method that utilization zero limit wave beam forms is without fuzzy restoring signal.These two kinds of methods are all being used real data, and obtain preferably result, yet these two kinds of methods are just for stripmap SAR.

In order to obtain more flexibly azimuth scene width and resolution, can pass through beam position SAR, such as Spotlight SAR Imaging, Sliding spotlight SAR or TOPS SAR etc. comes control resolution.Yet beam position SAR is in the process of data recording, and antenna direction changes, and causes the orientation bandwidth of whole data far above the signal transient bandwidth, has surpassed the requirement of strip-type hyperchannel SAR signal reconstruction.

For this problem, Nicolas etc. have proposed the method for reconstructing of a kind of " ladder ", and for the treatment of hyperchannel TOPSSAR data, the method utilizes sub-aperture imaging to process the hyperchannel TOPS SAR signal reconstruction problem that efficiently solves.Yet in processed in sub-aperture, little PRF can cause the orientation a lot of data blocks to occur, and caused complicated operation, chose with the data splicing of sub-aperture etc. such as overlapped data.In addition, the scallop phenomenon also can occur take PRF as the cycle.

Above method is the imaging processing problem of Solving Multichannel beam position SAR well.

Summary of the invention

The object of the invention is to the deficiency for above-mentioned prior art, the full aperture formation method of a kind of hyperchannel beam position SAR is provided, to realize the high-resolution imaging under the wide-scene.

The technical thought that realizes the object of the invention is: to receiving the echoed signal of original synthetic-aperture radar SAR, at orientation frequency domain and Beam Domain echoed signal is compressed processing, by using rear Doppler's space-time adaptive processing method that the echoed signal of azimuth ambiguity is recovered, and in conjunction with the doppler imaging algorithm to echoed signal carry out the correction of range migration and distance to, orientation to compression process, be embodied as picture.Concrete steps comprise as follows:

(1) adopt the channel mode full aperture of multicast to receive original SAR echoed signal;

(2) echoed signal is carried out orientation bandwidth reduction processing and wave beam compression processing;

2a) according to the echoed signal form, make up orientation bandwidth reduction function H ' (t _a, X _m) and wave beam compression function H (t _a, X _m) be:

$H(t_a,X_m)=\exp (-j2\mathrm{\π\α}(t_a-t_r)X_m-\mathrm{j\π\β}{X}_m^2),$

$H^{\′}(t_a,X_m)=\exp (-\mathrm{j\π\γ}{t}_a^2-j2\mathrm{\π}{t}_a{f}_r);$

Wherein, t _aBe slow time of orientation, X _mBe that m passage is to the orientation spacing of reference channel, t _rBe the direction reference time, a and β are unknown parameter, and exp is the exponential function take natural logarithm e the end of as, f _rBe the direction reference frequency, γ is unknown parameter;

2b) with echoed signal and orientation bandwidth reduction function H ' (t _a, X _m) and wave beam compression function H (t _a, X _m) multiply each other, obtain echoed signal at the expression S of orientation time domain-Beam Domain (t _a, X _m):

$S(t_a,X_m)=w_{\mathrm{ang}}\left(X_m\right)w_{\mathrm{azi}}(t_a+\frac{X_m}{2v}-t_0)\exp (-j\frac{4\mathrm{\π}}{\mathrm{\λ}}\sqrt{R_b^2+{(v{t}_c-v{t}_a-\frac{X_m}{2})}^2})$

$\×\exp (-j2\mathrm{\π\α}(t_a-t_r)X_m-\mathrm{j\π\β}{X}_m^2-\mathrm{j\π\γ}{t}_a^2-j2\mathrm{\π}{t}_a{f}_r)$

Wherein, w _Ang() is the channel weighting function, w _AziBe the orientation window function, τ is site in the phasing, t _cFor representing the time of target location, t ₀Be orientation time corresponding to Doppler's central point, R _bFor carrier aircraft arrives the scene minimum distance, λ is the echoed signal wavelength, and v is the carrier aircraft flying speed;

2c) to S (t _a, X _m) do two-dimensional Fourier transform, obtain echoed signal at the expression S of Doppler domain-angle domain (f _a, sin θ):

$S(f_a,\sin \mathrm{\θ})=\∫w_{\mathrm{azi}}(\mathrm{\τ}-t_0)\exp (-j\frac{4\mathrm{\π}}{\mathrm{\λ}}\sqrt{R_b^2+{(v{t}_c-\mathrm{v\τ})}^2})$

$\×\exp (-\mathrm{j\π\γ}{\mathrm{\τ}}^2-j2\mathrm{\π}(f_a+f_r)\mathrm{\τ})\mathrm{\Π}\left(\mathrm{\τ}\right)\mathrm{d\τ}$

Wherein, f _aBe the orientation frequency, θ be carrier aircraft to the target angle of squint, ∏ (τ) is intermediate variable and can being expressed as:

$\mathrm{\Π}\left(\mathrm{\τ}\right)=\∫w_{\mathrm{ang}}\left(x\right)\exp \left(j2\mathrm{\πx}(-\mathrm{\α}(\mathrm{\τ}-t_r)+\frac{\mathrm{\γ\τ}+f+f_a}{2v}-\frac{\sin \mathrm{\θ}}{\mathrm{\λ}})\right)$

$\×\exp \left(\mathrm{j\π}(\frac{\mathrm{\α}}{v}-\mathrm{\β}-\frac{\mathrm{\γ}}{4v^2})x^2\right)\mathrm{dx}$

Wherein x is transition parameter,

At this moment, parameter alpha, beta, gamma need satisfy:

2d) will

Among the substitution intermediate variable ∏ (τ), obtain:

$\mathrm{\Π}\left(\mathrm{\τ}\right)=W_{\mathrm{ang}}(\frac{\sin \mathrm{\θ}}{\mathrm{\λ}}-\frac{f_a}{2v}-(\frac{f_{\mathrm{ref}}}{2v}+\mathrm{\α}{t}_{\mathrm{ref}})-(\frac{\mathrm{\γ}}{2v}-\mathrm{\α})\mathrm{\τ})$

W wherein _Ang() is w _AngThe Fourier transform of (),

At this moment, parameter a, γ need satisfy

2e) utilize described

And in conjunction with echoed signal limit bandwidth inequality $B_i+|\frac{2v^2}{\mathrm{\λ}{R}_r}+\mathrm{\γ}|T_a\≤M\×\mathrm{PRF},$ Calculate parameter alpha, the numerical value of beta, gamma;

2f) with the parameter alpha that calculates, the numerical value substitution echoed signal of beta, gamma is at the expression S of Doppler domain-angle domain (f _a, sin θ) in, orientation bandwidth reduction and the wave beam compression of echoed signal can be finished;

(3) utilize rear Doppler's space-time adaptive processing method, the echoed signal after the compression is carried out restoration and reconstruction, the echoed signal that is restored after rebuilding is S (f _a):

$S\left(f_a\right)=\∫w_{\mathrm{azi}}(\mathrm{\τ}-t_0)\exp (-j\frac{4\mathrm{\π}}{\mathrm{\λ}}\sqrt{R_b^2+{(v{t}_c-\mathrm{v\τ})}^2})$

$\×\exp (-\mathrm{j\π\γ}{\mathrm{\τ}}^2-j2\mathrm{\π}{f}_r\mathrm{\τ}-j2\mathrm{\π}{f}_a\mathrm{\τ})\mathrm{d\τ}$

(4) echoed signal after the restoration and reconstruction is transformed to two-dimensional frequency, obtain the echoed signal S of two-dimensional frequency ₀(f _τ);

(5) utilize the doppler imaging algorithm to the echoed signal S of two-dimensional frequency ₀(f _τ) carry out range migration correction and pulse compression, be embodied as picture.

The present invention compared with prior art has following advantage:

1) the present invention be directed to the hyperchannel full aperture imaging technique of beam position SAR pattern, overcome existing hyperchannel full aperture imaging technique and be only limited to the stripmap SAR pattern, the problem that azimuthal resolution is lower, Effective Raise azimuthal resolution.

2) the present invention processes by the compression at orientation frequency domain and Beam Domain, has effectively solved the excessive problem of blur number that beam position SAR echoed signal orientation bandwidth causes much larger than instant bandwidth.

3) the present invention adopts full aperture to receive echoed signal, has avoided the new problem brought in the complex process such as piecemeal, splicing based on sub-aperture method and piecemeal, the splicing, has greatly simplified the imaging processing flow process, has improved treatment effeciency.

Description of drawings:

Fig. 1 is SAR formation method process flow diagram of the present invention;

Fig. 2 is the 2-d spectrum figure of original object echoed signal;

Fig. 3 is the 2-d spectrum figure after the compression of the wide compression of echoed signal classical prescription bit strip and wave beam among the present invention;

Fig. 4 be among the present invention the echoed signal after the compression through after 2-d spectrum figure after the Doppler's space-time adaptive processing;

Fig. 5 appoints to get the contour image of a point target from 9 point targets;

Fig. 6 uses the present invention to the imaging processing result of measured data.

Embodiment

With reference to Fig. 1, SAR imaging processing implementation step of the present invention is as follows:

Step 1 under beam position SAR pattern, is the challenge of avoiding sub-aperture piecemeal to bring, adopts the channel mode full aperture of multicast to receive original SAR echoed signal.

Step 2 is carried out orientation bandwidth reduction processing and wave beam compression processing to echoed signal, to solve the excessive problem of beam position SAR orientation bandwidth.

2a) according to the echoed signal form, make up orientation bandwidth reduction function H ' (t _a, X _m) and wave beam compression function H (t _a, X _m) be:

$H(t_a,X_m)=\exp (-j2\mathrm{\π\α}(t_a-t_r)X_m-\mathrm{j\π\β}{X}_m^2),$

$H^{\′}(t_a,X_m)=\exp (-\mathrm{j\π\γ}{t}_a^2-j2\mathrm{\π}{t}_a{f}_r);$

Wherein, t _aBe slow time of orientation, X _mBe that m passage is to the orientation spacing of reference channel, t _rBe the direction reference time, a and β are unknown parameter, and exp is the exponential function take natural logarithm e the end of as, f _rBe the direction reference frequency, γ is unknown parameter;

2b) with echoed signal and orientation bandwidth reduction function H ' (t _a, X _m) and wave beam compression function H (t _a, X _m) multiply each other, obtain echoed signal at the expression S of orientation time domain-Beam Domain (t _a, X _m):

$S(t_a,X_m)=w_{\mathrm{ang}}\left(X_m\right)w_{\mathrm{azi}}(t_a+\frac{X_m}{2v}-t_0)\exp (-j\frac{4\mathrm{\π}}{\mathrm{\λ}}\sqrt{R_b^2+{(v{t}_c-v{t}_a-\frac{X_m}{2})}^2})$

$\×\exp (-j2\mathrm{\π\α}(t_a-t_r)X_m-\mathrm{j\π\β}{X}_m^2-\mathrm{j\π\γ}{t}_a^2-j2\mathrm{\π}{t}_a{f}_r)$

Wherein, w _Ang() is the channel weighting function, w _AziBe the orientation window function, τ is site in the phasing, t _cFor representing the time of target location, t ₀Be orientation time corresponding to Doppler's central point, R _bFor carrier aircraft arrives the scene minimum distance, λ is the echoed signal wavelength, and v is the carrier aircraft flying speed;

2c) to S (t _a, X _m) do two-dimensional Fourier transform, obtain echoed signal at the expression S of Doppler domain-angle domain (f _a, sin θ):

$S(f_a,\sin \mathrm{\θ})=\∫w_{\mathrm{azi}}(\mathrm{\τ}-t_0)\exp (-j\frac{4\mathrm{\π}}{\mathrm{\λ}}\sqrt{R_b^2+{(v{t}_c-\mathrm{v\τ})}^2})$

$\×\exp (-\mathrm{j\π\γ}{\mathrm{\τ}}^2-j2\mathrm{\π}(f_a+f_r)\mathrm{\τ})\mathrm{\Π}\left(\mathrm{\τ}\right)\mathrm{d\τ}$

Wherein, f _aBe the orientation frequency, θ be carrier aircraft to the target angle of squint, ∏ (τ) is intermediate variable and can being expressed as:

$\mathrm{\Π}\left(\mathrm{\τ}\right)=\∫w_{\mathrm{ang}}\left(x\right)\exp \left(j2\mathrm{\πx}(-\mathrm{\α}(\mathrm{\τ}-t_r)+\frac{\mathrm{\γ\τ}+f+f_a}{2v}-\frac{\sin \mathrm{\θ}}{\mathrm{\λ}})\right)$

$\×\exp \left(\mathrm{j\π}(\frac{\mathrm{\α}}{v}-\mathrm{\β}-\frac{\mathrm{\γ}}{4v^2})x^2\right)\mathrm{dx}$

Wherein x is transition parameter,

At this moment, parameter alpha, beta, gamma need satisfy:

2d) will

Among the substitution intermediate variable ∏ (τ), obtain:

$\mathrm{\Π}\left(\mathrm{\τ}\right)=W_{\mathrm{ang}}(\frac{\sin \mathrm{\θ}}{\mathrm{\λ}}-\frac{f_a}{2v}-(\frac{f_{\mathrm{ref}}}{2v}+\mathrm{\α}{t}_{\mathrm{ref}})-(\frac{\mathrm{\γ}}{2v}-\mathrm{\α})\mathrm{\τ})$

W wherein _Ang() is w _AngThe Fourier transform of (),

At this moment, parameter a, γ need satisfy

2e) utilize described

And in conjunction with echoed signal limit bandwidth inequality $B_i+|\frac{2v^2}{\mathrm{\λ}{R}_r}+\mathrm{\γ}|T_a\≤M\×\mathrm{PRF},$ Calculate parameter a, the numerical value of beta, gamma;

2f) with the parameter alpha that calculates, the numerical value substitution echoed signal of beta, gamma is at the expression S of Doppler domain-angle domain (f _a, sin θ) in, orientation bandwidth reduction and the wave beam compression of echoed signal can be finished.

Step 3, Doppler's space-time adaptive processing method after utilizing carries out restoration and reconstruction to the echoed signal after the compression, and the echoed signal that is restored after rebuilding is S (f _a):

$S\left(f_a\right)=\∫w_{\mathrm{azi}}(\mathrm{\τ}-t_0)\exp (-j\frac{4\mathrm{\π}}{\mathrm{\λ}}\sqrt{R_b^2+{(v{t}_c-\mathrm{v\τ})}^2})$

$\×\exp (-\mathrm{j\π\γ}{\mathrm{\τ}}^2-j2\mathrm{\π}{f}_r\mathrm{\τ}-j2\mathrm{\π}{f}_a\mathrm{\τ})\mathrm{d\τ},$

Described rear Doppler's space-time adaptive processing method is referring to Z.F.Li, H.Y.Wang, T.Su, and Z.Bao, " Generation of wide-swath and high-resolution SAR images from multichannel smallspaceborne SAR systems, " IEEE Geosci.Remote Sens.Lett., vol.2, no.1, pp.82-86, Jan.2005

Step 4 transforms to two-dimensional frequency with the echoed signal after the restoration and reconstruction.

4a) with the orientation frequency f _aWith a new coordinate variable τ _aExpression, i.e. f _a=-γ * τ _a, with f _a=-γ * τ _aEchoed signal S (f after the substitution restoration and reconstruction _a) in, obtain echoed signal S (the γ τ after the conversion _a);

4b) according to (the γ τ of the echoed signal S after the conversion _a), structure phase function h (τ _a):

$h\left({\mathrm{\τ}}_a\right)=\exp (-\mathrm{j\π\γ}{\mathrm{\τ}}_a^2);$

4c) with (the γ τ of the echoed signal S after the conversion _a) and phase function h (τ _a) multiply each other, obtain the new expression S (τ of echoed signal _a):

$\begin{array}{c}S\left({\mathrm{\τ}}_a\right)=\∫w_{\mathrm{azi}}(\mathrm{\τ}-t_0)\exp (-j\frac{4\mathrm{\π}}{\mathrm{\λ}}\sqrt{R_b^2+{(v{t}_c-\mathrm{v\τ})}^2})\\ \×\exp (-\mathrm{j\π\γ}{(\mathrm{\τ}-{\mathrm{\τ}}_a)}^2-j2\mathrm{\π}{f}_r\mathrm{\τ})\mathrm{d\τ}\end{array};$

4d) to described S (τ _a) make Fourier transform, obtain the frequency domain representation formula S (f of echoed signal _τ), and to phase function h (τ _a) make Fourier transform, and get its conjugation, obtain frequency domain phase function H (f _τ);

4e) with the frequency domain representation formula S (f of echoed signal _τ) and frequency domain phase function H (f _τ) multiply each other, obtain the echoed signal S of two-dimensional frequency ₀(f _τ).

Step 5 for concrete beam position SAR pattern, utilizes corresponding doppler imaging algorithm to the echoed signal S of two-dimensional frequency ₀(f _τ) carry out range migration correction and pulse compression, be embodied as picture.

Under different beam position SAR patterns, can adopt different doppler imaging algorithms that the two-dimensional frequency echoed signal is carried out range migration correction and process of pulse-compression.For example: for the Spotlight SAR Imaging pattern, can adopt the frequency modulation of matched filtering MF algorithm or expansion to become mark ECS algorithm; Can adopt analysis of spectrum SPECAN algorithm for Sliding spotlight SAR pattern and TOPS SAR pattern.

So far, the full aperture formation method of hyperchannel beam position SAR is finished substantially.

Below further specify validity of the present invention by point target emulation experiment and measured data imaging processing.

One, point target emulation experiment

1. simulated conditions:

Simulation parameter such as table one:

Table one: analogue system major parameter

Carrier frequency	9.65GHz
		Effective velocity	6800m/s
Frequency span	18MHz
		The launching beam width	0.33 degree
Integration time	1.1s
		Instant bandwidth	2519.6Hz
The rotation center distance	-298km
		The scene center linear distance	596.1km
The orientation bandwidth	7690.8Hz
		Pulse repetition rate	900Hz

2. emulation content:

Use the present invention 9 point targets are carried out the imaging simulation experiment.

The 2-d spectrum figure of 9 point target original echoed signals as shown in Figure 2 in the emulation experiment.

Emulation 1, original echoed signals is carried out the Beam Domain compression in application the present invention and angle domain is compressed, and the echoed signal 2-d spectrum figure after the compression is as shown in Figure 3.

Emulation 2 is used the present invention the echoed signal after compressing is carried out rear Doppler's space-time adaptive processing, and the echoed signal 2-d spectrum figure after the processing as shown in Figure 4.

Emulation 3 is processed the back echo signal to rear Doppler's space-time adaptive and is carried out range migration correction and pulse compression, is embodied as picture, and appoints and get the contour image of a point target, as shown in Figure 5.

3. analysis of simulation result:

As can be seen from Figure 2, exist azimuth spectrum fuzzy in the point target original echoed signals, and fuzzy number is larger;

As can be seen from Figure 3, after application the present invention carried out Beam Domain compression and angle domain compression to original echoed signals, the echoed signal azimuth ambiguity made moderate progress, and fuzzy number reduces;

As can be seen from Figure 4, after application the present invention carried out rear Doppler's space-time adaptive processing to the echoed signal after compressing, there was not azimuth ambiguity in echoed signal, and echoed signal obtains correct restoration and reconstruction;

As can be seen from Figure 5, application the present invention is respond well to the focal imaging of point target.

Two, measured data imaging processing

1. imaging processing condition:

Use the present invention and the measured data of a certain airborne triple channel TOPS SAR pattern carried out imaging processing, parameter such as the table three of this measured data acquisition system:

Table three: system's major parameter

Carrier frequency	16.2GHz
		Effective velocity	71m/s
Frequency span	40MHz
		The launching beam width	5.3 degree
Integration time	6s
		Instant bandwidth	730Hz
The rotation center distance	-600km
		The scene center linear distance	12.11km
The orientation bandwidth	6169Hz
		Pulse repetition rate	333Hz
Sampling rate	62.5MHz

2. imaging processing interpretation of result:

Use the present invention described measured data is carried out imaging processing, imaging processing result uses as can be seen from Figure 6 the present invention and can realize wide-scene, high-resolution imaging as shown in Figure 6.

Claims (2)

1. the full aperture formation method of a hyperchannel beam position SAR comprises the steps:

(1) adopt the channel mode full aperture of multicast to receive original SAR echoed signal;

(2) echoed signal is carried out orientation bandwidth reduction processing and wave beam compression processing;

2a) according to the echoed signal form, make up orientation bandwidth reduction function H ' (t _a, X _m) and wave beam compression function H (t _a, X _m) be:

$H(t_a,X_m)=\exp (-j2\mathrm{\π\α}(t_a-t_r)X_m-\mathrm{j\π\β}{X}_m^2),$

$H^{\′}(t_a,X_m)=\exp (-\mathrm{j\π\γ}{t}_a^2-j2\mathrm{\π}{t}_a{f}_r);$

Wherein, t _aBe slow time of orientation, X _mBe that m passage is to the orientation spacing of reference channel, t _rBe the direction reference time, a and β are unknown parameter, and exp is the exponential function take natural logarithm e the end of as, f _rBe the direction reference frequency, γ is unknown parameter;

2b) with echoed signal and orientation bandwidth reduction function H ' (t _a, X _m) and wave beam compression function H (t _a, X _m) multiply each other, obtain echoed signal at the expression S of orientation time domain-Beam Domain (t _a, X _m):

$S(t_a,X_m)=w_{\mathrm{ang}}\left(X_m\right)w_{\mathrm{azi}}(t_a+\frac{X_m}{2v}-t_0)\exp (-j\frac{4\mathrm{\π}}{\mathrm{\λ}}\sqrt{R_b^2+{(v{t}_c-v{t}_a-\frac{X_m}{2})}^2})$

$\×\exp (-j2\mathrm{\π\α}(t_a-t_r)X_m-\mathrm{j\π\β}{X}_m^2-\mathrm{j\π\γ}{t}_a^2-j2\mathrm{\π}{t}_a{f}_r)$

Wherein, w _Ang() is the channel weighting function, w _AziBe the orientation window function, τ is site in the phasing, t _cFor representing the time of target location, t ₀Be orientation time corresponding to Doppler's central point, R _bFor carrier aircraft arrives the scene minimum distance, λ is the echoed signal wavelength, and v is the carrier aircraft flying speed;

2c) to S (t _a, X _m) do two-dimensional Fourier transform, obtain echoed signal at the expression S of Doppler domain-angle domain (f _a, sin θ):

$S(f_a,\sin \mathrm{\θ})=\∫w_{\mathrm{azi}}(\mathrm{\τ}-t_0)\exp (-j\frac{4\mathrm{\π}}{\mathrm{\λ}}\sqrt{R_b^2+{(v{t}_c-\mathrm{v\τ})}^2})$

$\×\exp (-\mathrm{j\π\γ}{\mathrm{\τ}}^2-j2\mathrm{\π}(f_a+f_r)\mathrm{\τ})\mathrm{\Π}\left(\mathrm{\τ}\right)\mathrm{d\τ}$

Wherein, f _aBe the orientation frequency, θ be carrier aircraft to the target angle of squint, ∏ (τ) is intermediate variable and can being expressed as:

$\mathrm{\Π}\left(\mathrm{\τ}\right)=\∫w_{\mathrm{ang}}\left(x\right)\exp \left(j2\mathrm{\πx}(-\mathrm{\α}(\mathrm{\τ}-t_r)+\frac{\mathrm{\γ\τ}+f+f_a}{2v}-\frac{\sin \mathrm{\θ}}{\mathrm{\λ}})\right)$

$\×\exp \left(\mathrm{j\π}(\frac{\mathrm{\α}}{v}-\mathrm{\β}-\frac{\mathrm{\γ}}{4v^2})x^2\right)\mathrm{dx}$

Wherein x is transition parameter,

At this moment, parameter alpha, beta, gamma need satisfy:

2d) will

Among the substitution intermediate variable ∏ (τ), obtain:

$\mathrm{\Π}\left(\mathrm{\τ}\right)=W_{\mathrm{ang}}(\frac{\sin \mathrm{\θ}}{\mathrm{\λ}}-\frac{f_a}{2v}-(\frac{f_{\mathrm{ref}}}{2v}+\mathrm{\α}{t}_{\mathrm{ref}})-(\frac{\mathrm{\γ}}{2v}-\mathrm{\α})\mathrm{\τ})$

W wherein _Ang() is w _AngThe Fourier transform of (),

At this moment, parameter a, γ need satisfy

2e) utilize described

And in conjunction with echoed signal limit bandwidth inequality $B_i+|\frac{2v^2}{\mathrm{\λ}{R}_r}+\mathrm{\γ}|T_a\≤M\×\mathrm{PRF},$ Calculate parameter alpha, the numerical value of beta, gamma;

2f) with the parameter alpha that calculates, the numerical value substitution echoed signal of beta, gamma is at the expression S of Doppler domain-angle domain (f _a, sin θ) in, orientation bandwidth reduction and the wave beam compression of echoed signal can be finished;

(3) utilize rear Doppler's space-time adaptive processing method, the echoed signal after the compression is carried out restoration and reconstruction, the echoed signal that is restored after rebuilding is S (f _a):

$S\left(f_a\right)=\∫w_{\mathrm{azi}}(\mathrm{\τ}-t_0)\exp (-j\frac{4\mathrm{\π}}{\mathrm{\λ}}\sqrt{R_b^2+{(v{t}_c-\mathrm{v\τ})}^2})$

$\×\exp (-\mathrm{j\π\γ}{\mathrm{\τ}}^2-j2\mathrm{\π}{f}_r\mathrm{\τ}-j2\mathrm{\π}{f}_a\mathrm{\τ})\mathrm{d\τ}$

(4) echoed signal after the restoration and reconstruction is transformed to two-dimensional frequency, obtain the echoed signal S of two-dimensional frequency ₀(f _τ);

(5) utilize the doppler imaging algorithm to the echoed signal S of two-dimensional frequency ₀(f _τ) carry out range migration correction and pulse compression, be embodied as picture.

2. the full aperture formation method flow process of the hyperchannel beam position SAR described in according to claim 1, wherein step (4) is described transforms to two-dimensional frequency with the echoed signal after the restoration and reconstruction, obtains the echoed signal S of two-dimensional frequency ₀(f _τ), carry out as follows:

4a) with the orientation frequency f _aWith a new coordinate variable τ _aExpression, i.e. f _a=-γ * τ _a, with f _a=-γ * τ _aEchoed signal S (f after the substitution restoration and reconstruction _a) in, obtain echoed signal S (the γ τ after the conversion _a);

4b) according to (the γ τ of the echoed signal S after the conversion _a), structure phase function h (τ _a):

$h\left({\mathrm{\τ}}_a\right)=\exp (-\mathrm{j\π\γ}{\mathrm{\τ}}_a^2);$

4c) with (the γ τ of the echoed signal S after the conversion _a) and phase function h (τ _a) multiply each other, obtain the new expression S (τ of echoed signal _a):

$\begin{array}{c}S\left({\mathrm{\τ}}_a\right)=\∫w_{\mathrm{azi}}(\mathrm{\τ}-t_0)\exp (-j\frac{4\mathrm{\π}}{\mathrm{\λ}}\sqrt{R_b^2+{(v{t}_c-\mathrm{v\τ})}^2})\\ \×\exp (-\mathrm{j\π\γ}{(\mathrm{\τ}-{\mathrm{\τ}}_a)}^2-j2\mathrm{\π}{f}_r\mathrm{\τ})\mathrm{d\τ}\end{array};$

4d) to described S (τ _a) make Fourier transform, obtain the frequency domain representation formula S (f of echoed signal _τ), and to phase function h (τ _a) make Fourier transform, and get its conjugation, obtain frequency domain phase function H (f _τ);

4e) with the frequency domain representation formula S (f of echoed signal _τ) and frequency domain phase function H (f _τ) multiply each other, obtain the echoed signal S of two-dimensional frequency ₀(f _τ).

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